Mix Vermiculite and Perlite?

[hungng]

I'm close to pouring my insulating layer under the hearth and have just realized I need another bag of vermiculite. I was going to get another 100 litre bag but I've just discovered that perlite is mined not far from here and is much cheaper. If I buy a 100 litre bag of perlite can I mix it with the vermiculite? Will the combination make a strong enough base for the oven to sit on and if I do get the perlite, should I get medium or course grain?

Thanks for your help.

[Neil2]

Yes. You can mix them. I find that the perlite added to the vermiculite actually aids in placement and workability.

Try to get the coarse grain.